1. Technical Field
The invention relates to a method of machining a substrate to divide the substrate such as a wafer, which includes a laser-machining process such as scribing, and to a method of manufacturing a chip.
2. Related Art
For example, when chips having elements are manufactured from a substrate (wafer), there is a process for cutting the substrate, such as a silicon wafer, to divide the substrate into a plurality of chips. In this case, for example, there is a method of rotating a grindstone by dicing, cutting, and dividing the substrate. However, since this method uses liquid such as water and grinding fluid, this method cannot be used when elements which should not be wet are divided.
There is a laser-machining method of irradiating a laser beam to machine and divide a substrate in a predetermined shape. Particularly, in case of a laser-machining process, there are a method of cutting the substrate by forming grooves in desired portions, modifying property to be brittle, or expanding stress (for example, tension stress, bending stress, thermal stress, and the like) to break down the substrate, and a method of applying heat (energy) to melt a predetermined portion and cutting it (for example, JP-A-2002-192367 (FIGS. 1 and 2), JP-A-2002-205180 (FIGS. 1 and 2)).
However, in case of the laser-machining process, when there is a portion which should not be machined by a laser beam, for example, a step or a T-shaped portion, a high-precision laser-machining process and a high-precision laser-machining apparatus are required so as not to machine the portion. Accordingly, in case of the laser-machining process, which can not secure the high-precision, it is difficult to perform the laser-machining process.